Respiratory apparatus



1963 R. e. BARTLETT, JR 3,099,987

RESPIRATORY APPARATUS Filed March '7, 1961 2 Sheets-Sheet l FIG. 2

INVENTOR. Rosco/5 G. EARTLETT JR.

BY m gf ,4 TTORNEY Aug. 6, 1963 R. G. BARTLETT, JR

RESPIRATORY APPARATUS 2 Sheets-Sheet 2 Filed March 7, 1961 INVENTOR.EbJcoE 6.5.4R7'L ErTJR. BY

141 TORWE Y more, such devices have United States Patent ()1 3,099,987RESPTORY APPARATUS Roscoe G. Bartlett, IL, Lillian, Ala. Filed Mar. 7,1961, Ser. No. 94,090 1 Claim. (Cl. 128-142) (Granted under Title 35,US. Code (1952), sec. 266) The invention described herein may bemanufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of any royaltiesthereon or therefor.

This invention relates generally to respiratory apparatus as is employedin high altitudes and is particularly concerned with the transfer ofmoisture from expired to inspired breath for the purpose of humidifyingany respirant which may be furnished to the user.

The use of oxygen at high altitudes is a known requirement for thecontinuation of animal life. Studies of the physiology of respirationhave shown that for each altitude there is a minimum concentration ofoxygen which must be provided in the fluid breathed if normaloxygenation of the blood is to be maintained. This necessaryconcentration of oxygen for various altitudes has been determinedapproximately as follows: 20% at sea level; 27.5% at 10,000 feet; 50% at20,000 feet; 60 at 25,000 feet; 80% at 30,000 feet; and 100% at 34,000feet and above.

To prevent the freezing of valves and other components of the oxygendelivery equipment, both the liquid and compressed forms of this gas aresupplied to the user in as dry a form as possible. All possible watervapor has been removed. Prolonged breathing of such dry oxygen isfrequently accompanied by respiratory discomfort as a result of thedesiccation of the mucous membranes which produces irritation, coughing,sore throats, head colds and other deleterious effects on these delicatelinings of the respiratory tracts.

In order to prevent these respiratory diflioulties due to the dryoxygen, a reliable means of adding moisture thereto was mandatorilyrequired. Although adequate humidification of the inspired dry oxygencould be easily accomplished by passing it over or through water, thismethod has the disadvantages of additional weight due to the necessaryequipment, limited duration of use, and the necessity of carrying asupply of water. Under the exigencies of high altitude operations,whether mountain climbing or aviation, including space travel, theadditional weight features become highly important and are practicallyprohibitive for the use of such extra equipment and supplies.

Other prior art devices have included an attempt to solve this problem.Such partial solutions have included socalled rebreather bags orvariously shaped canisters for the collection of moisture from theexpired breath. These devices, however, have defeated their purpose bynot making such moisture available to the dry oxygen being inspired,i.e., moisture has only been present in that portion of the inspirationdue to rebreathed air, and, furtheraided the collect-ion of the moistureby gravity, at least, in the lower portions of the bags and canisterswhere it quickly became unavailable for any use.

The principal object of my invention, therefore, is to provide areliable, simple, and self-contained means for humidifying the entireportion of fluid being inspired.

Another object of my invention is to provide a simple humidifier whichcan easily be adapted to known equipment.

A further object of my invention is to provide a device by whichsufiicient moisture from the expired breath is recycled to the inspireddry oxygen to produce a relative humidity of approximately 70% in theinspired breath.

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A still further object of my invention to produce a breath humidifierwhich is self-priming, self-regulating, and whose operation is notlimited in time nor is it dependent upon the renewal of an expendablesubstance.

Other and further objects of my invention will be better understood inconnection with the following detailed description and the accompanyingdrawings wherein:

FIGURE 1 is a side elevation of a breathing mask incorporating myinvention;

FIG. 2. is a front elevation, partly broken away and partly in sectionof the mask and its valving arrangements taken on the line 2-2 of FIG.1;

FIG. 3 is another view of the valving arrangement taken on the line 33of FIG. 1;

FIG. 4 is an enlarged elevation in cross-section of certain details ofmy invention taken on the line 4-4 of FIG. 2;

FIG. 5 is an enlarged view of the expiratory valve shown in FIG. 4 inthe open position; and

FIGS. 6 and 7 are schematic views illustrating the operation of myinvention.

With reference to FIGS. 1, 2, and 3, the mask 10 which is usedprincipally as a means for insuring a reasonably airtight seal with theusers mouth, nose, and face, carries a container 12 which is filled withmoisture exchange material 14. The valve structure 16 includes anexpiratory valve 18 and an inspiratory valve 20. The usual corrugatedflexible tube 22 for the transmission or delivery of the pressurizedoxygen is shown attached to the inspiratory valve structure 20* byengaging the tubular enxension 24. While expiratory valve 18 may be ofthe simple check valve type, it is best constructed in the form shown asa pressure compensated type having a sensing tube 26 leading from theexternal valve chamber 28 to the inflow tubular extension 24-.

With reference particularly to FIGS. 3-5, inclusive, the container 12may be a cylindrical body of metal, plastic, or other suitable materialadapted at one end to be inserted in the mask 10, as into the annularshape 11, and suitably detachably secured at the other end to the valvestructure 16. Screens 13 are secured at each end of the container 12 forsuitably confining the moisture exchange material 14 therein. Valvefoundation plate 17 with its overlying gasket 19 serves as the mainconnection structure between the mask and container combination and thevalve structures. This plate 17 has two large circular holes 21 whichserve to channel the expired and inspired fluids through theirrespective Valves.

Expiratory valve 18 has a valve base ring 30, an annular supportingmember 3 1, a plurality of distance pieces 32 inserted between base ring30 and supporting member 31, flexible gasket 33 and a pressure chamberdefining member or cap portion 34. These parts are suitably heldtogether and to valve foundation plate 17 by the machine screws 35.Between base ring 30 and the flexible gasket 33, valve plate 36 andvalve plate support 37 are supported by the flexible gasket 33. Valveplate 36 consists of a planar front plate 38 and an annular ring 39formed integrally on the back of front plate 38. Base ring 30 isprovided with annular knife edge 40 on which the planar portion of frontplate 38 rests when the valve is closed. Valve plate support 37 iscupped forwardly, as shown, and is provided with a comparatively massivehub 41. The cup portion of support 37 receives telescopically theannular back ring 39 of valve plate 36 whereby this part 36 is guidedand supported. Hub 41 fits into a centrally formed aperture in theflexible gasket 33. The gasket may be cemented to the hub 41 and thusforms a flexible support for the working valve parts 36 and 37. A lightcoil compression spring 42 fits into the expansion cylinder formed bythe ring and cup portions of valve parts 36 and 37 and serves to keepvalve plate 36 tightly on the knife edge valve seat 40 when the breathis being inspired.

The cap member 34 is provided with an enlarged concentric bore 43 and asmaller extending bore 44. These bores form the pressure chamber 28previously mentioned. Bore 43 contains a light coil compression spring45 which operates on the flexible gasket 33. Smaller bore 43 serves asan extension of the sensing tube 26 and transmits the pressurized fluidto the back of the flexible gasket 33.

As shown in FIGS. 4 and 5, when the user is inspiring, the valve plate38 rests on the knife edge 40 by virtue of the pressures of springs 42and 45 and the fluid pressure in chamber 28. Upon expiration, valveplate 36 is forced open and the air escapes as shown by the arrows 46 inFIG. 5. Coil springs 42 and 45 are compressed and flexible gasket 33 ismoved outwardly against the pressure of spring 45 and the fluid pressurein chamber 28. Thus, with the fluid pressure acting on the back of theworking valve parts, compensation is provided for the use of higherrespirant pressures necessitated by unusual demand or extremely highaltitudes.

Inspiratory valve 20 comprises a cylinder 47 of metal, plastic, or othersuitable material having an enlarged bore 48 and a smaller bore definedby the tubular extension 24. This cylinder 47 is suitably secured to thevalve foundation plate 17 by the screws and nuts 52. A valve supportplate 49, having a central aperture 50 and a plurality of apertures 51symmetrically disposed with relation to cen tral aperture 50, iscemented or otherwise suitably secured at the shoulder joining the twobores in the cylinder 47. Apertures 51 are for the inward passage of thepressurized respirant being inspired. Central aperture 50 receives thesupporting plug 53 of the valve part 54. Valve part 54 and plug 53 areintegrally formed of rubber or some other suitable flexible material notaffected by the chemical nature of the respirant nor the possiblyextremely low ambient temperatures. When the respirant is beinginspired, the valve part 54 flexes inwardly as shown in phantom at 55,FIG. 4, thus allowing the respirant free passage through the apertures51.

In the preferred embodiment of my invention, as thus far described, themoisture exchange material 14 is 20 grams of large crystals (38 mesh) ofsilica gel. During expiration moisture is trapped by surface absorptionon the silica gel crystals. During the subsequent inspiration, thismoisture is readily released to the dry inspired respirant. Althoughsilica gel is frequently used as a desiccant, its reaction with moistureis a purely physical one and when moist silica gel is exposed to a drygas, the moisture is quickly and practically totally released. Smallercrystals than the 3-8 mesh specified above provide a greater moistureexchange but increase the resistance to air flow. Crystal size,therefore, must be a compromise which permits free air flow whileproviding also a surface large enough for eflicient moisture exchange.

While silica gel crystals were used in this preferred embodiment due toits inertness, relative stability, Wide availability and cheapness,there are doubtless numbers of other chemicals or substances which couldserve the function of moisture exchange here disclosed. Such substancescould include quantities of precious or semi-precious stones, crystalsof silicon carbide or other suitable refractories, or suitably sizedcrystals of any other material chemically inert to the respirant beingused and not subject to disintegration during use whether due to thereaction of the respirant on the material or the mechanical flow of thegas.

FIGS. 6 and 7 illustrate schematically the use of my improved device.FIG. 6 shows the sequence of events during expiration. Here the entireexpired breath is passing through and over the moisture exchangematerial in canister 12 before being exhausted to the atmosphere throughthe expiratory valve 18. A great percentage of the moisture in theexpired breath is thus deposited on the crystals of the moistureexchange material. FIG. 7 depicts the respirant being inspired. Thisincoming fluid passes generally over the moisture exchange material and,being very dry, picks up practically all the moisture present on thesurface of the exchange material. In this case, of course, theinspiratory valve opens and the expiratory valve closes. It should benoted again that, in my device, the moisture exchange material is in thepaths of the entire fluid flow, both expiratory and inspiratory.

In actual quantitative tests of my invention, each test lasting for aperiod of six hours, it was found that a complete equilibrium wasestablished after the first few breaths and that thereafter there waslittle change in the magnitude of the moisture exchange for a givensubject. Individual subjects showed small, but unimportant, variationsin the extent of the moisture exchange and these, it is assumed, whereattributable to different breathing patterns. Considering all subjects,there was a moisture exchange of between 60 and with most values fallingnear 70%. Although there are no previous data on which to base acomparison, it is believed that this level of humidification should bequite conducive to comfort and safety when breathing pure oxygen from adry source for prolonged periods of time.

Having thus described a preferred embodiment of my invention, I do notintend to be limited thereby as the structures and materials shown maybe subject to many modifications by those skilled in the art. All suchmodifications are considered as falling within the spirit of theinvention and the scope of the appended claim wherein I claim:

A respiratory apparatus for users of pressurized respirant comprising:

a face mask adapted to sealingly cover the mouth and nose of the user;

a first conduit leading from said mask for passing all of the expiredand inspired fluids from and to the lungs and respiratory passages ofthe user;

a second conduit leading out of said first conduit;

a third conduit leading out of said first conduit;

a source of pressurized respirant attached to said third conduit;

a moisture transfer means wholly contained within said first conduit,said moisture transfer means consisting of a container adapted to besealingly secured at one end to said face mask and to form said firstconduit, a quantity of granular material adapted to collect condensedmoisture on the surfaces thereof and to allow said moisture to evaporatetherefrom enclosed within said container, a screen at each end of saidcontainer for retaining said granular material therein, and a perforatedvalve plate on the other end of said container, said valve plateaflording connection means from said first conduit to said second andthird conduits;

an inspiratory check valve supported by said perforated valve plate insaid third conduit for controlling the influx of said respirant to saidfirst conduit and mask; and

an expiratory check valve supported by said perforated valve plate insaid second conduit for allowing the controlled escape of expired fluidto atmosphere, said expiratory check valve consisting of an annular basering having a circular knife edge extending outwardly therefrom, saidbase ring forming said second conduit, an annular support member spacedoutwardly from said base ring, a plurality of hollow cylindricaldistance pieces separating said base ring and said support member, a capportion mounted concentrically and outwardly of said support member,said base ring, distance pieces, support member and cap portion beingsecured together with fastening means passing therethrough, a flexiblegasket mounted between said support member and said cap portion, a cupshaped valve support member held by said flexible gasket, the cupportion thereof extending inwardly toward said base ring, a valveengaging said base ring knife edge, said valve having an annular ringformed on its outward side, said annular ring fitting telescopically inthe cup portion of said valve member whereby said valve is held insliding juxtaposition to said knife edge, a compression spring mountedbetween said valve and valve support member for normally pressing saidvalve adjacent said knife edge, and means for pressurizing the outwardside of said flexible gasket from said 6 third conduit whereby theoperation of said expiratory valve is controlled by the fluid pressureof said respirant.

References Cited in the file of this patent UNITED STATES PATENTS1,710,160 Gibbs Apr. 23, 1929 FOREIGN PATENTS 1,172,206 France Oct. 13,1958 1,121,482 France Apr. 30, 1956

